Rapid emplacement of the Central Atlantic Magmatic Province as a net sink for CO2

Abstract

Recent evidence from the~201.5 Ma Central Atlantic Magmatic Province (CAMP) in the Newark rift basin demonstrates that this Large Igneous Province produced a transient doubling of atmospheric pCO 2 , followed by a falloff to pre-eruptive concentrations over~300 kyr. This paper confirms the short-term findings from the Newark basin, and tests the million-year effects of the CAMP volcanism on Early Jurassic pCO 2 from strata in the corollary Hartford basin of Eastern North America (ENA) also using the pedogenic carbonate paleobarometer. We find pCO 2 levels for pre-CAMP background of 2000 ±700 ppm (at S(z)=3000±1000 ppm), increasing to~5000±1700 ppm immediately above the first lava flow unit, consistent with observations from the Newark. The longer post-extrusive Portland Formation of the Hartford basin records a fourth pulse of pCO 2 to~4500 ± 1200 ppm, about 240 kyr after the last lava recorded in the ENA section. We interpret this fourth increase as due to a major episode of volcanism, and revise the main CAMP duration to 840 ± 60 kyr. The Portland also records a post-eruptive decrease in pCO 2 reaching pre-eruptive background concentrations of~2000 ppm in only~300 kyr, and continuing to levels below pre-CAMP background over the subsequent 1.5 Myr following the final episode of eruptions. Geochemical modeling (using modified COPSE code) demonstrates that the rapidity of the pCO 2 decreases, and fall to concentrations below background can be accounted for by a 1.5-fold amplification of the continental silicate weathering response due to the presence of the CAMP basalts themselves. These results demonstrate that a continental flood basalt capable of producing a short-term perturbation of the carbon system may actually have an overall netcooling effect on global climates due to a long-term net-decrease in pCO 2 to below pre-eruptive levels, as previous models have suggested followed the emplacement of the Deccan Traps.

Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years

“…26), indicating that wildfires cannot be the sole source of the variations. The observed relationship between δ 13 C and floral change, wildfires, and overall climate variability is set against the backdrop of unusually high atmospheric CO 2 over the interval we sampled (27). We calculated atmospheric pCO 2 from multiple stable carbon isotope analyses of soil carbonate and preserved organic matter, (27,35,40); error bars represent S(z) = 3,000 ± 1,000 ppm (see SI Appendix, SI Text, for details).…”

Modulation of Late Cretaceous and Cenozoic climate by variable drawdown of atmospheric <i>p</i>CO<sub>2</sub> from weathering of basaltic provinces on continents drifting through the equatorial humid belt

“…In fact, continental LIPs are likely to be net CO 2 sinks due to enhanced consumption from their weathering Schaller et al, 2012).…”

“…CAMP basalts were apparently thin (100-200 m-thick) but emplaced over a large area across tropical Pangea (5-10 Mkm 2 ; Marzoli et al, 1999;McHone 2003), and only minor exposures of lavas in isolated rift basins and widely scattered presumed feeder dikes now remain (McHone, 2003). The bulk of the CAMP lavas were probably weathered, eroded or buried soon after their emplacement, very likely within a few hundred thousand years of volcanic activity as suggested by estimates of atmospheric pCO 2 from paleosols interbedded and overlying CAMP lavas in eastern North America (Schaller et al, 2012) and tantalizing indications of rapid global cooling (Schoene et al, 2010). In any case, we suppose that any remaining exposed CAMP fragments were probably too small or had already drifted out of the equatorial humid belt to be important factors in weathering CO 2 consumption by Cretaceous times.…”

Climatic disaster at the Triassic-Jurassic boundary - a clay minerals and major elements record from the Polish Basin

“…Ris ing at mo spheric car bon di ox ide con cen tra tions likely caused global cli mate changes and a Late Rhaetian super-green house (McElwain et al, 1999;White side et al, 2010;Schaller et al, 2011Schaller et al, , 2012Steinthorsdottir et al, 2011). Brief but ex treme green house events may have been re lated to mas sive in jec tions of iso to pi cally light car bon from oce anic meth ane hy drate destabilization and its cu mu la tive in put into the at mo sphere and ocean (Beerling and Berner, 2002;Hesselbo et al, 2000Hesselbo et al, , 2007.…”

“…Some au thors, though, have re cently chal lenged the causal link be tween end-Tri as sic meth ane re lease and ter res trial eco sys tem cri sis . In deed, the green house ef fect as a single cause of ter res trial ex tinc tions is chal lenged by many authors, who em pha size en vi ron men tal stress caused by emission of volcanogenic toxic com pounds, soil acid i fi ca tion and suc ces sive rapid cli ma tic re ver sals (Self et al, 2006;Ganino and Arndt, 2009;Schootbrugge et al, 2009;Racki, 2010;Pieñkowski et al, 2012Pieñkowski et al, , 2014Schaller et al, 2012). More over, it was found that at mo spheric CO 2 con cen tra tions had increased ear lier in the Rhaetian (Cleve land et al, 2008;.…”